A four-arm small molecule compound and a preparation method and application thereof
By preparing four-armed small molecule additives, the active layer structure of organic solar cells was optimized, solving the problems of dosage control and residual hazards of DIO in organic solar cells, and achieving high-efficiency and stable organic solar cell performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGHAN UNIVERSITY
- Filing Date
- 2025-12-25
- Publication Date
- 2026-07-03
AI Technical Summary
In existing technologies, the use of DIO additives in organic solar cells presents challenges such as difficulty in controlling the dosage, significant residual hazards, and insufficient environmental compatibility, which affect device performance and stability, and make it difficult to achieve high power conversion efficiency.
Using four-armed small molecule additives, compounds with three-dimensional molecular geometry were prepared through Suzuki coupling, acetalization, Vilsmeier haack acylation, deprotection, and Knoevenage condensation reactions. This optimized the stacking behavior, inhibited molecular aggregation, and promoted three-dimensional charge transport.
High efficiency and long-term stability of organic solar cells were achieved by optimizing phase separation morphology and charge transport, improving power conversion efficiency to 18.63%, and simplifying the synthesis process.
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Figure CN121378282B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of organic solar cell technology, and in particular to a four-armed small molecule compound, its preparation method, and its application. Background Technology
[0002] Achieving high power conversion efficiency (PCE) in organic solar cells (OSCs) hinges on the construction of a nanoscale, bicontinuous interpenetrating network structure with donor / acceptor materials reaching thicknesses of hundreds of nanometers. This unique architecture is crucial for ensuring effective exciton dissociation and efficient synchronous carrier transport. However, due to the significant differences in the inherent physicochemical properties of the donor and acceptor materials, relying solely on the original processing solvent often fails to achieve the optimal active layer morphology required for high-efficiency devices. This has become a major bottleneck restricting the improvement of OSC performance.
[0003] Against this backdrop, additive-assisted strategies, due to their high efficiency and simplicity, have become a core technical approach for optimizing the morphology of the active layer. This strategy fully utilizes the advantages of additives: such as high boiling point characteristics that can regulate solvent evaporation rates, selective solubility that can guide phase separation behavior, and specific intermolecular interactions that can adjust molecular packing patterns. This allows for precise control of the active layer's microstructure, including optimizing molecular packing order, regulating the uniformity of vertical component distribution, and controlling the scale and extent of phase separation, thus laying a solid foundation for the high performance of OSCs.
[0004] In the morphology regulation of the active layer of organic solar cells, the classic additive 1,8-diiodooctane (DIO) exhibits selective effects on different acceptor materials: for fullerene acceptors PCBM, DIO can effectively inhibit the formation of large aggregates in the blend film through selective dissolution; while for non-fullerene acceptors ITIC, due to their extremely poor solubility in DIO, the introduction of DIO will promote the aggregation and phase separation process of ITIC.
[0005] Although DIO exhibits regulatory value in specific systems, its application still faces several key challenges: First, dosage control is difficult; excessive addition can lead to excessive aggregation of the acceptor phase, forming large domains exceeding 50 nm in size, while exciton diffusion length is typically less than 10 nm. These large domains severely hinder exciton diffusion efficiency. Second, residual hazards are significant. As a high-boiling-point solvent additive (boiling point reaches 276℃), DIO is difficult to completely volatilize during processing. Residual DIO can trigger a series of negative effects: it can induce molecular rearrangement within the active layer, leading to a decrease in long-term device stability; it can also corrode electrode materials such as Al, damaging the electrochemical stability of the interface layer; and it can excessively enhance the crystallinity of the donor material, causing excessively dense molecular chain stacking, which in turn inhibits charge transport. Third, environmental compatibility is insufficient. As a halogen-based additive, DIO poses potential hazards to the ecological environment.
[0006] Given the challenges mentioned above, developing environmentally friendly green additives to simultaneously improve the power conversion efficiency and long-term stability of organic solar cells has become a core technical challenge that urgently needs to be overcome in this field. Summary of the Invention
[0007] The purpose of this invention is to address the aforementioned shortcomings of the prior art by providing a four-armed small molecule additive that optimizes stacking behavior and reduces energy disorder. The three-dimensional molecular geometry endows the cross-shaped molecule with unique properties, particularly inhibiting molecular aggregation behavior and establishing three-dimensional charge transport properties through a quasi-isotropic pathway.
[0008] The first objective of this invention is to provide a four-armed small molecule additive material, wherein the structure of the active layer additive material is shown in Formula I:
[0009] .
[0010] The second objective of this invention is to provide a method for preparing a four-armed small molecule additive material, characterized by comprising the following steps:
[0011] S1. Starting from benzo[1,2-b:4,5-b']dithiophene-4,8-diylbis(trifluoromethanesulfonate), compound 2 was obtained by Suzuki coupling reaction with 5-(4,4,5,5-tetramethyl-1,3,2-dioxoboron-2-yl)thiophene-2-carboxaldehyde.
[0012] ;
[0013] S2. Compound 2 is reacted with 2,2-dimethyl-1,3-propanediol and p-toluenesulfonic acid acetalization protection to give compound 3:
[0014] ;
[0015] S3 and compound 3 undergo a Vilsmeier-Haack acylation reaction with n-butyllithium to give compound 4:
[0016] ;
[0017] S4 and compound 4 undergo a deprotection reaction with trifluoroacetic acid to give compound 5:
[0018] ;
[0019] S5, compound 5, and Knoevenage condensation with 3-hexyl-2-thiothiazolidin-4-one yielded a four-armed small molecule compound 4B:
[0020] .
[0021] Furthermore, the molar ratio of the compound benzo[1,2-b:4,5-b']dithiophene-4,8-diylbis(trifluoromethanesulfonate) to 5-(4,4,5,5-tetramethyl-1,3,2-dioxoborane-2-yl)thiophene-2-carboxaldehyde is 1:(1~5). Preferably, it is 1:3.5.
[0022] Furthermore, the molar ratio of compound 2 to 2,2-dimethyl-1,3-propanediol is 1:(2~6), and the molar ratio of compound 2 to p-toluenesulfonic acid is 1:(0.01~0.05). Preferably, it is 1:0.04.
[0023] Furthermore, the molar ratio of compound 3 to n-butyllithium is 1:(1~3). Preferably, it is 1:2.6.
[0024] Furthermore, the molar ratio of compound 4 to trifluoroacetic acid is 1:(2~3). Preferably, it is 1:2.5.
[0025] Furthermore, the molar ratio of compound 5 to 3-hexyl-2-thiothiazolidin-4-one is 1:(5~15). Preferably, it is 1:10.
[0026] A third objective of this invention is to provide an active layer for an organic solar cell, wherein the active layer contains a four-armed small molecule compound as described above.
[0027] Furthermore, the active layer includes a donor PM6 and an acceptor L8-BO, and the content of the four-armed small molecule compound accounts for 0.1~0.46% of the active layer.
[0028] A fourth objective of this invention is to provide an organic solar cell device, comprising, in sequence, an ITO substrate, a PEDOT:PSS layer, an active layer, a PDINN layer, and an electrode; the active layer is as described above.
[0029] Compared with the prior art, the present invention has the following beneficial effects:
[0030] (1) A four-armed small molecule compound was added as an additive to the active layer. This additive was introduced into the OSC to optimize packing behavior and reduce energy disorder. Crystallization kinetics were critically modulated, promoting the formation of interconnected, interpenetrating networks within the membrane, and achieving a PCE of 18.63%. This configuration provides a three-dimensional molecular geometry, endowing the cross-shaped molecule with unique properties, particularly inhibiting molecular aggregation behavior and establishing three-dimensional charge transport properties through a quasi-isotropic pathway. The four-armed molecule acts as a grain to improve interaction with PM6, promoting high packing order in the blended film. Therefore, it can enhance… J SC And FF. Promotes the formation of good phase separation morphology and high-purity structural domains, which is conducive to the construction of high-quality interpenetrating networks, achieving more efficient and balanced carrier transport, effectively promoting exciton dissociation and suppressing charge recombination.
[0031] (2) The novel four-armed small molecule additive designed by the present invention is a key way to achieve synergistic control of nanoscale phase separation morphology and photophysical process, inhibits excessive polymer aggregation, promotes the formation of a bicontinuous interpenetrating network of donor-acceptor, and balances exciton dissociation and charge transport efficiency, thereby enabling the preparation of high-efficiency organic solar cells.
[0032] (3) The synthesis process provided by the present invention is simple and easy to purify, and has good prospects for practical application. Attached Figure Description
[0033] Figure 1 Compound 2 prepared in this invention 1 H NMR spectrum;
[0034] Figure 2 Compound 3 prepared in this invention 1 H NMR spectrum;
[0035] Figure 3 Compound 4 prepared in this invention 1 H NMR spectrum;
[0036] Figure 4 Compound 4B prepared in this invention 1 H NMR spectrum;
[0037] Figure 5The current density-voltage ratio of the organic solar energy device prepared for this invention JV )test;
[0038] Figure 6 The external quantum efficiency (EQE) test result is shown for the organic solar energy device prepared in this invention. Detailed Implementation
[0039] To more clearly explain the technical solution and beneficial effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the described accompanying drawings are only some embodiments of the present invention and are used only to explain the present invention, and should not be construed as limiting the present invention. Unless otherwise specified, the equipment and reagents used in the present invention are commercially available products conventional in this technical field.
[0040] Unless otherwise specified, the "water" used in the following examples is deionized water.
[0041] In the following tests of this invention, proton nuclear magnetic resonance (NMR) spectra were performed on an AVANCE NEO 400MHz NMR spectrometer from Bruker GmbH, Germany. The solvent used was deuterated chloroform (CDCl3), and the instrument was calibrated with tetramethylsilane (TMS).
[0042] Liquid chromatography was performed using a Shimadzu LCMS-2010EV liquid chromatography-mass spectrometry system.
[0043] Example 1
[0044] The synthetic route for the four-armed small molecule compound is as follows:
[0045] The specific process is as follows:
[0046] .
[0047] (1) Synthesis of compound 2:
[0048] Under nitrogen protection, benzo[1,2-b:4,5-b']dithiophene-4,8-diylbis(trifluoromethanesulfonate) (5 g, 10.30 mmol), 5-(4,4,5,5-tetramethyl-1,3,2-dioxoboron-2-yl)thiophene-2-carboxaldehyde (8.57 g, 36 mmol), palladium acetate (200 mg), and 2-dicyclohexylphosphine-2',4',6'-triisopropylbiphenyl (600 mg) were added to a flask. Tetrahydrofuran (60 mL) and distilled water (2 mL) were then added, and the mixture was stirred at 90 °C for 15 h. After cooling to room temperature, the mixture was poured into water, filtered, and washed with distilled water and methanol, respectively. The residue was dried to give compound 2 as a yellow-green solid (3.9 g, 92.4% yield). ¹H NMR (400 MHz, CDCl₃) δ (ppm) 10.04 (s, 2H), 7.94 (d, J = 3.8 Hz, 2H), 7.63 -7.59 (m, 4H), 7.56 (d, J = 5.7 Hz, 2H). The spectrum of compound 2 is shown below. Figure 1 As shown.
[0049] (2) Synthesis of compound 3
[0050] Compound 2 (3.90 g, 9.5 mmol), 2,2-dimethyl-1,3-propanediol (4.94 g, 47.5 mmol), and p-toluenesulfonic acid (65 mg, 0.38 mmol) were added to a flask under a nitrogen atmosphere. Toluene (50 mL) was then added, and the mixture was stirred at 130 °C for 12 h. After cooling to room temperature, the mixture was poured into water, filtered, and washed with distilled water and methanol, respectively. The residue was dried to obtain compound 3 as a pale yellow solid (4.62 g, 83.4% yield). The 1H NMR spectrum of compound 3 is shown below. Figure 2 shown. 1HNMR (400 MHz, CDCl3) δ 10.08 (s, 2H), 8.34 (s, 2H), 7.42 (d, J = 3.6 Hz, 2H), 7.32 (d, J = 3.6 Hz, 2H), 5.76 (s, 2H), 3.83 (dt, J = 11.4, 1.4 Hz, 4H), 3.72(d, J = 11.0 Hz, 4H), 1.33 (s, 6H), 0.84 (s, 6H).
[0051] (3) Synthesis of compound 4
[0052] Compound 3 (4.00 g, 6.86 mmol) was dissolved in tetrahydrofuran (50 mL) under a nitrogen atmosphere. After stirring for 10 min in an ice-salt bath, n-butyllithium (7.13 mL, 17.84 mmol) was added dropwise. After stirring for another 40 min, N,N-dimethylformamide (10 mL) was added, and stirring was continued for another 25 min. The mixture was quenched with water, extracted with ethyl acetate, dried over anhydrous sodium sulfate, and purified by column chromatography with dichloromethane:methanol (20:1) to give compound 4 as a yellow solid (3.5 g, 79.9% yield). 1 H NMR (400 MHz, CDCl3) δ (ppm): 10.08 (s, 2H), 8.34 (s, 2H), 7.42 (d, J = 3.6 Hz, 2H), 7.32 (d, J = 3.6 Hz, 2H), 5.76 (s, 2H), 3.83 (dt, J = 11.4, 1.4 Hz, 4H), 3.72 (d, J = 11.0 Hz, 4H), 1.33 (s, 6H), 0.84 (s, 6H) of compound 4 1 H NMR spectrum as shown Figure 3 As shown.
[0053] (4) Synthesis of compound 5
[0054] Under a nitrogen atmosphere, compound 4 (3.50 g, 5.49 mmol) and trifluoroacetic acid (1.56 g, 13.7 mmol) were added to a flask. Dichloromethane (60 mL) was then added, and the mixture was stirred at 40 °C for 12 h. After cooling to room temperature, a saturated sodium bicarbonate solution was added until no more bubbles were produced. The pH of the solution was adjusted to neutral, and the mixture was filtered. The solution was washed with distilled water and methanol, respectively, to give compound 5 as an orange solid (1.80 g, 70.3% yield).
[0055] (5) Synthesis of the four-armed small molecule compound 4B
[0056] Under a nitrogen atmosphere, compound 5 (1.80 g, 3.86 mmol), 3-hexyl-2-thiothiazolidin-4-one (8.38 g, 38.60 mmol), chloroform (30 mL), and piperidine (1 mL) were added to a flask and reacted at 70 °C for 12 h. After cooling to room temperature, the reaction was quenched with water, extracted with ethyl acetate, dried over anhydrous sodium sulfate, and column-secreted with dichloromethane:petroleum ether = 1:1 to give compound 4B as a blue-black powder (2.00 g, yield 41.7%). The four-armed small molecule compound 4B... 1 H NMR spectrum as shown Figure 4Shown: 1H NMR (400 MHz, Chloroform-d) δ 7.94 (d, J = 2.9 Hz, 2H), 7.81 (d, J = 13.0 Hz, 4H), 7.58 (d, J = 2.9 Hz, 4H), 4.10 (dt, J = 29.9, 8.0 Hz, 8H), 1.83 – 1.68 (m, 8H), 1.34 (d, J = 15.6 Hz, 24H), 0.96 – 0.84 (m, 12H).
[0057] Example 2
[0058] Characterization of small molecule organic solar cell devices.
[0059] Fabrication of organic photovoltaic devices:
[0060] The organic solar cell device comprises, in sequence, an ITO substrate, a PEDOT:PSS layer, an active layer, a PDINN layer, and electrodes.
[0061] (1) After ultrasonic cleaning, ITO glass (indium tin oxide conductive glass) is treated with oxygen-Plasma. PEDOT:PSS poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (Xi’an Yuri Solar Energy Technology Co., Ltd., PEDOT:PSS AI4083, product number: 306020, a mixed solution prepared at the time of purchase) is first spin-coated on ITO at 5000 rpm. The substrate is annealed at 150℃ for 15 minutes to obtain a substrate with a surface film thickness of about 40 nm.
[0062] (2) Then, the donor material PM6 and the acceptor L8-BO (structure shown below) are mixed to form a binary organic solar energy device (the mass ratio of donor and acceptor materials and additives is preferably 0.99:1.2:0.01). A mixed solvent of diiodomethane and chloroform (the volume ratio of diiodomethane to chloroform is 0.3 μL:100 μL) is added to prepare a blend solution (the total concentration of donor and acceptor is 20 mg / mL). The blend solution is coated onto the substrate in step (1) at a spin coating speed of 2000 rpm. An active layer with a thickness of about 130 nm is coated on the surface of the substrate.
[0063] (3) The substrate obtained in step (2) was placed in a 60 nm culture dish. Then, 60 μL of chlorobenzene was evenly coated on its surface and annealed with solvent vapor (85 °C, 5 min). Next, an electron transport layer PDINN film was coated on the active layer at a spin coating speed of 3000 rpm. Finally, a 100 nm thick silver layer was deposited on top of the electron transport layer by vapor deposition.
[0064] The specific solar cell efficiencies are shown in Table 1 (the equipment used in the laboratory of this invention was a solar simulator, calibrated with silicon solar cells, and all tests were conducted under simulated sunlight, 100 mW / cm²). 2 ).
[0065]
[0066]
[0067]
[0068] As can be seen from the data in Table 1, the four-armed small molecule compound 4B prepared in this invention, when used as an additive in OSCs with PM6:L8-BO as the active layer, improves the photoelectric conversion efficiency of binary photovoltaic devices. This type of polymer additive has unique advantages in organic solar cells and in the commercialization of organic solar cells.
[0069] Table 1. Photovoltaic parameters for optimal performance of devices with or without metal-type coordination polymers.
[0070]
[0071] The donor PM6 and acceptor L8-BO were mixed to prepare a binary organic solar energy device (the donor and acceptor materials and their mass ratio were preferably 1:1). Then, 4B prepared in Example 1 was added as an additive to the binary device with an active layer of PM6:L8-BO to prepare organic solar energy devices (the preferred mass ratio of PM6:L8-BO:4B was 0.99:1.2:0.01). PM6:L8-BO and 4B served as a control group. The JV curve was then measured under simulated sunlight (at 100 mW / cm² on a solar simulator (SAN-EI, XES-40S2-CE)). 2 The current-voltage (JV) characteristics were measured using a Keithley 2450 source meter under an irradiation intensity of (AM 1.5G).
[0072] The results are as follows Figure 5 As shown in the figure, the performance of the four-armed small molecule compound 4B prepared in this invention is significantly improved when added to PM6:L8-BO compared to PM6:L8-BO. In photodynamic analysis, it can be found that the device with the four-armed small molecule material 4B added to PM6:L8-BO has a larger exciton diffusion coefficient and a faster exciton dissociation process compared to the device based on PM6:L8-BO.
[0073] like Figure 6The figure shows the external quantum efficiency (EQE) test results: the EQE spectrum was analyzed using a certified Newport IPCE measurement system. High-sensitivity EQE was measured using an integrated system (PECT-600, Enlitech), where the photocurrent is amplified and modulated via a locked instrument. This test corroborates that the EQE spectrum of the PM6:L8-BO device with added 4B is consistent with the values obtained from the integrated Jsc vs. JV curves of the solar spectrum (AM 1.5 G) compared to that of the PM6:L8-BO-based device, with an error of less than 5%. This means that adding 4B to the device allows for more efficient internal charge transfer and the generation of more charge carriers.
[0074] For any points not covered above, existing technologies shall apply.
[0075] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.
Claims
1. A four-armed small molecule compound, characterized in that, The structural formula of the four-armed small molecule compound is shown in Formula I: 。 2. A method for preparing a four-armed small molecule compound as described in claim 1, characterized in that, Includes the following steps: S1. Starting from compound 1, compound 2 was obtained by a Suzuki coupling reaction with 5-(4,4,5,5-tetramethyl-1,3,2-dioxoboran-2-yl)thiophene-2-carboxaldehyde: ； The structural formula of compound 1 is as follows: ； S2. Compound 2 is reacted with 2,2-dimethyl-1,3-propanediol and p-toluenesulfonic acid acetalization protection to give compound 3: ； S3 and compound 3 undergo a Vilsmeier-Haack acylation reaction with n-butyllithium to give compound 4: ； S4 and compound 4 undergo a deprotection reaction with trifluoroacetic acid to give compound 5: ； S5, compound 5, and Knoevenage condensation with 3-hexyl-2-thiothiazolidin-4-one yielded the four-armed small molecule compound 4B: 。 3. The preparation method according to claim 2, characterized in that, The molar ratio of compound 1 to 5-(4,4,5,5-tetramethyl-1,3,2-dioxoborane-2-yl)thiophene-2-carboxaldehyde is 1:(3.5~5).
4. The preparation method according to claim 2, characterized in that, The molar ratio of compound 2 to 2,2-dimethyl-1,3-propanediol is 1:(2~6), and the molar ratio of compound 2 to p-toluenesulfonic acid is 1:(0.01~0.05).
5. The preparation method according to claim 2, characterized in that, The molar ratio of compound 3 to n-butyllithium is 1:(2.6~3).
6. The preparation method according to claim 2, characterized in that, The molar ratio of compound 4 to trifluoroacetic acid is 1:(2~3).
7. The preparation method according to claim 2, characterized in that, The molar ratio of compound 5 to 3-hexyl-2-thiothiazolidin-4-one is 1:(5~15).
8. An active layer of an organic solar cell, characterized in that, The active layer contains the tetra-armed small molecule compound as described in claim 1.
9. The active layer of the organic solar cell as described in claim 8, characterized in that, The active layer includes the donor PM6 and the acceptor L8-BO, and the content of the four-armed small molecule compound accounts for 0.1~0.46% of the active layer.
10. An organic solar cell device, characterized in that, It comprises, in sequence, an ITO substrate, a PEDOT:PSS layer, an active layer, a PDINN layer, and an electrode; the active layer is as described in claim 8 or 9.